This invention relates to signal networks, and more particularly to signal networks for interconnecting multi-media apparatus.
According to computer industry estimates there are over 40 million homes in the United States with personal computers (PCs), and nearly half of these homes have more than one PC. The forecast is that these numbers will double in five years. Surveys of consumers with multiple PCs indicate that, in terms of priority, they want the PCs to be able to share files, printers, modems and the Internet, followed by the sharing of other peripheral equipment and the playing of network games. These shared applications require minimum signal transfer rates of 1 Mb/s for satisfactory performance.
Similarly, more than 73 million homes nationwide are subscribers to cable television (CATV). The CATV services provide installed coaxial cable in one or more rooms of a house, resulting in the majority of subscribers having more than one television receiver (TV). Additionally, the expansion of CATV services to include internet access (i.e. xe2x80x9cdata over cable system interface specificationxe2x80x9d or DOCSIS) and the advent of consumer electronic products for internet use as well as for entertainment purposes, all promote a desire to network this equipment for shared use Networking allows a PC in the home office to print documents on a printer in the family room, a VCR in the family room to be remotely controlled to display video on a kitchen TV, and a wireless computer keyboard used with the family room TV to access work or game files on the PC in the home office. The alternative to networking is product duplication.
There is of course a cost associated with establishing a network. This is the cost of installing the network wiring and the cost of purchasing and installing any interface devices which are necessary to adapt the appliances for network operation. The current CEBus Standard installation guide for home networks specifies installation of a central distribution box (xe2x80x9cService Centerxe2x80x9d) which receives all of the network signals, both internal and external. External signals include radio frequency (RF) broadband signals from CATV, satellite dishes, and antenna received broadcastxe2x80x94collectively xe2x80x9cRF broadcast signalsxe2x80x9d, as well as DOCSIS. The internal signals are those from the networked appliances, including digital signals from digital signal apparatus, such as computers, computer peripheral equipment, telephones and facsimile machines, as well as RF modulated video signals produced by RF modulation of audio/video output signals from the networked multimedia A/V equipment.
To accommodate these different network signal forms and to permit bi-directional signal transmission between appliances via the distribution box (i.e. downstream and upstream transmission) the Standard specifies installation of dual coaxial cables and one or more Category 5 twisted pair (TP) copper wires from the Service Center to outlets in each equipment room of the house. Upstream signal transmission includes the RF modulated A/V signals from the network multimedia equipment which the interface devices provide over CATV channel frequencies reserved by the owner for internal use. The downstream coax signals include both RF broadcast signals, control signals, and the home user RF modulated A/V signals. The baseband, digital signal devices, including computers, modems, faxes and digital telephones communicate over the twisted pair. The present estimated cost of installing CEBus Standard network wiring in new home construction is approximately $1 per square foot, and the estimated cost of upgrading existing homes is 2 to 3 times as much.
Alternatively, considering the broad installed base of CATV services and the fact that there are an additional 30 million homes with CATV access, it is desirable to provide for networking of the electronic appliances in a home through the installed CATV cabling. As known, CATV services provide a source signal connection to the home from a xe2x80x9chead endxe2x80x9d, or local node of the service provider""s CATV system. Within the house the signals are distributed from this head end connection through coaxial cables, which include a single conductor plus a shield. Signal splitters are used to divide the source CATV signal among the cables thereby providing the source CATV signal with a substantially constant load impedance, while also providing signal isolation between its output ports to prevent signals propagating from the source connection from being cross coupled to the other output ports. The splitter, therefore, prevents the upstream transmission necessary required for network communications, which is the reason for the dual cable requirement of the CEBus Standard.
One object of the present invention is to provide bi-directional signal transmission over a single conductor coaxial cable. Another object of the present invention is to provide a network capable of conducting simultaneous bi-directional signal transmission of unmodulated digital signals, and radio frequency (RF) modulated signals over a single conductor coaxial cable. Still another object of the present invention is to provide a network capable of providing bi-directional signal transmission of broadband, baseband and infrared signals over a single conductor coaxial cable. Still another object of the present invention is to provide bi-directional transmission of high bandwidth broadband signals over a low bandwidth single conductor coaxial cable.
According to the present invention, a network includes one or more single conductor coaxial cables routed within proximity to one or more local groups of networked appliances, interface apparatus associated with each networked appliance which use frequency division to separate the computer and media signals from the local group appliances onto baseband and broadband signal frequency channels within a local coaxial cable which couples the signals to a central distribution unit apparatus. The distribution apparatus (unit) receives all of the local cables and couples the baseband and broadband channel signals of each cable, into each other local cable, to cause the baseband and broadband signals from each networked appliance to be made available to each other appliance.
In further accord with the present invention, the distribution unit or apparatus further receives RF broadcast television signals which it mixes into the broadband signal channel of each local cable, thereby additionally making the RF broadcast signals available to each networked appliance concurrently with the baseband and broadband signals from each other appliance. In still further accord with the present invention, each interface apparatus includes bi-directional frequency filters for exchanging the computer and media signals from the appliances with the signals from the baseband and broadband signal channels of the local cable. In a still further accord with the present invention the distribution unit apparatus includes a signal bus for cross coupling the baseband and broadband signals among the local cables, the bus having a signal path geometry which minimizes signal interference within the baseband and broadband frequency channels due to signal reflections occurring within the network single.
The present invention provides a fully functional network over signal conductor coaxial cable, such as that presently used in CATV installations, thereby making network performance available at a significantly reduced cost. The invention includes the use of a novel signal distribution unit which interconnects the individual coaxial cables to the CATV signal source connection without the use of signal splitters or signal combiners. The network incorporates a multi-master approach with respect to the networked appliances. The network provides for computer signal speeds of 1.0 Mbps, a 125 Kbps signal speed for infrared control, and up to 158 television channels. The network also provides the network user with the choice of up to sixteen broadcast channels to be reserved for use within the home for audio/video transfer to any room having cable access. These reserved channels may be used for DVD, VCR, DSS, PC, cable box, video camera, security camera, CD jukebox, Home Control, laser disk, web TV, and video games.
Another important feature of the distribution unit or apparatus is the active amplification the unit provides to the broadcast and CATV signals received. Since the majority of the presently installed base of CATV is RG-59 coaxial cable with limited band width of approximately 500 MHz, this means that the subscriber cannot receive television channel broadcast above channel 70. The distribution unit compensates for this by adding active gain which amplifies the broadcast television signal by as much as 15 dB for the high end channel frequencies.
These and other objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying Drawing.